Fix max_active_tis_per_dag for deferred task instances

[SakshamSinghal20]

closes: #61700

Description

Deferred tasks were previously excluded from max_active_tis_per_dag and max_active_tis_per_dagrun concurrency checks. This allowed an unlimited number of tasks to enter the DEFERRED state, bypassing configured limits.

This PR enforces these limits for DEFERRED task instances while ensuring that max_active_tasks (which limits worker slot usage) remains unaffected.

Changes:

• airflow/ti_deps/dependencies_states.py: Introduced TASK_CONCURRENCY_EXECUTION_STATES to include DEFERRED, RUNNING, and QUEUED.
• airflow/jobs/scheduler_job_runner.py: Updated ConcurrencyMap to count deferred TIs for task-level limits, but explicitly exclude them from dag_run_active_tasks_map.
• airflow/models/taskinstance.py: Updated get_num_running_task_instances to count deferred TIs for pre-execution dependency checks.

Tests:

Added unit tests covering:

• Deferred tasks blocking new scheduling attempts.
• Mixed state scenarios (Running + Deferred).
• Regression checks ensuring max_active_tasks is not impacted.

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• closes: max_active_tis_per_dag not enforced for deferred task instances #61700